If he is actually obviously trolling, just report the post. Trolling is not allowed in these forums.
This, and one can stop it in their own thread. Stopping it overall on the forums isn't that easy/possible.
How would you stop trolling on the internet?
Not a 100% sure that's true, I don't know about trolling, but if he's spamming you he could certainly be reported for that, calling it trolling though is wrong that's more like harassment and blackmail, you find users like this end up digging their own graves because they resort to spamming you especially if they get put on the ignore list because they don't like the fact they aren't getting any attention.